Heretofore, ultraviolet (UV) absorbents having a benzotriazole or benzophenone skeleton have been used as additives to medical and cosmetic compositions as well as resin compositions.
However, these compounds that have a benzotriazole or benzophenone skeleton and are useful as UV absorbents suffered from various problems. Specifically the amount of the absorbents blended into a composition was limited due to their poor dispersion and solubility in base compounds. Moreover, bleeding could occur due to their dispersion instability.
Various proposals were made for improving the dispersion and dissolution of these compounds. For example, Japanese Patent Application Laid-open (JP-A) Nos. 21391/1982, 21432/1982, 10591/1983, 213075/1983, 111360/1986, and 187740/1987 disclose compounds of benzotriazole or benzophenone skeleton having alkoxysilyl groups incorporated therein. Due to the presence of alkoxysilyl groups, these compounds are susceptible to hydrolysis and lack stability. Medical and cosmetic compositions having these compounds blended therein have an unpleasant feel since the hydrolyzed products of these compounds are stimulative to the skin and mucous membranes.
For further improvement in stability, hydrolysis resistant compounds were proposed as disclosed in Japanese Patent Publication No. 50074/1977, JP-A 230681/1988, and Japanese Patent Application Nos. 64485/1989 and 12874/1990, for example. These compounds are unsusceptible to hydrolysis, but oily and less likely to form films.
JP-A 21391/1982 discloses a method for forming films by applying compounds having a benzotriazole or benzophenone skeleton to plastics and subjecting the compounds to hydrolysis to form films. This method is less consistent since film forming rate and film state vary with the surrounding atmosphere. Also, a hygienic problem occurs since alcohols are generated upon film formation.
There is a need for developing UV absorbing compounds free of the above-mentioned problems.